In gas circuit breakers, a fixed arc contact and a moving arc contact are provided in a tank filled with an insulating gas. By allowing the moving arc contact to move to a position where the moving arc contact contacts the fixed arc contact and a position where the moving arc contact is separated from the fixed arc contact, current can be injected into the conductors provided in the tank and the current flowing to the conductors can be interrupted.
When current is injected or interrupted, the gas circuit breaker blows an insulating gas in the tank to an arc generated between the moving arc contact and the fixed arc contact so as to extinguish the arc. Hence, a puffer chamber that stores gas to be blown to the arc is provided around the moving arc contact. By increasing the gas pressure of the insulating gas in the puffer chamber upon generation of an arc, a high-pressure insulating gas is blown to the arc. A higher gas pressure in the puffer chamber upon generation of an arc results in a higher arc-extinguishing performance and thus a higher current interruption performance of the gas circuit breaker.
Hence, an arc extinction assisting portion formed of an ablation material, such as perfluoroether-based polymers, that evaporates by the heat generated upon generation of an arc may be provided in the tank. When the arc extinction assisting portion evaporates upon generation of an arc and evaporative gas generated is taken into the puffer chamber, the gas pressure in the puffer chamber is increased. Consequently, the arc-extinguishing performance of the gas circuit breaker is improved. It is said in general that the arc-extinguishing performance is improved by providing an arc extinction assisting portion near the arc generation point. Patent Literature 1 discloses a technique in which an arc extinction assisting portion is provided in part of a nozzle placed near the arc generation point.